Method of tanning hides and skins



Patented Jan. 19, 1932 PATENT MATTHEW M. MERRITT, OF LIIDDLETON, MASSACHUSETTS, ASSIGNOR, BY MFSNE. AS-

SIGNMENTS, TO THE TANNING PROCESS COMPANY, OF BOSTON, MASSACHUSETTS, A

CORPORATION OF MASSACHUSETTS METHOD OF TANNING HIDES AND SKINS No Drawing.

This invention relates to improvements in methods of treating hides and skins with liquid substances. More particularly, the invention relates to improved methods of tanning both hides and skins.

In the tanning of hides and skins in accordance with methods which have been practised for many years, a great deal of time is consumed in handling the hides and skins and in preparing and disposing of great quantities of tanning liquors, and very considerable power is utilized in runningdrums and driving paddles in vats. Also, because of the repeated handling of hides and skins, a great deal of laborious and disagreeable work is performed by laborers whose wages amount to considerable sums and constitute a large part of the costs of tanning hides and skins. Furthermore, an important factor in the costs of leather manufacturing is the amount of capital involved in tanning operations as heretofore conducted, and the relatively slow turnover due to the length of time that must elapse between the receipt of the raw stock and the delivery of the finished product. Other disadvantages of the old and wellknown methods employed in both vegetable and mineral tannages, reside in the difiiculty of securing uniformly good tanning results and in the lack of any provision for protecting the important grain side of the raw hides and skins from injury during the first part of their treatment in vats, paddles, and drums.

Objects of this invention are to secure better and more uniform results in tanning operations, to shorten very materially the time consumed in tanning hides and skins, to improve the quality of the tanned hides and skins and to increase the yield of leather from hides and skins, to simplify the methods heretofore employed in tanning the various kinds of hides and skins, to lessen the handling of the stock, and to conserve tanning materials.

T o the ends, and in accordance with an important characteristic of the invention, a strong or concentrated solution of tanning material is applied directly to one or both surfaces of a raw hide or skin after it has been stretched out in fully extended condition Application filed October 24, 1929. Serial No. 402,319.

with all folds and wrinkles or creases efiaced particularly from the grain surface. For best results, the tanning material is allowed to give a set to the fibers thereofwhile it is in the described extended condition, whereby the smooth appearance of the grain surface and the area of the spread-out hide or skin will be maintained during operations for completing the tanning of the hide or skin. Hence, the hide or skin does not subsequently shrink as it does during tanning by previously known methods where the shrinkage may be as much as 20%, thus necessitating other operations in attempts to recover this loss in area. In the preferred practise of this improved method of tanning, each hide or skin will be slicked-out in extended condition upon a smooth supporting surface, since this operation secures a smooth grain surface and the full, normal area of each hide or skin which is maintained through atmospheric pressure and adhesion of the hide or skin to the smooth supporting surface While tanning material is being applied and acting on the hide or skin. Preferably, the hide or skin is slicked-out with the grain surface facing upwardly and to this surface there is applied a limited amount of a fresh strong or concen-,

trated tanning solution which instantly tans the grain surface of the hide or skin and gives it a fine uniform color. Immediately,

after this application of tanning solution the hide or skin is stripped from the smooth sup: porting surface and placed with the grain surface facing downwardly upon the same or a similar supporting surface after which the piece of work is slicked-out a second time. There is then applied to the flesh surface of the hide or skin a limited amount of a strong or concentrated tanning solution sufficient,

to act on the hide or skin for a time suflicient when, acting in conjunction with that applied to the grain surface, to strike through the hide or skin. The hide or skin thus treated not only maintains its extended area but is actually thicker and plumper than a hide or skin tanned by the old methods. I

While, as stated, it is preferred to slick the skin out upon a smooth supporting surface, good results may be obtained by passing the skins through a wringing machine or a putting-out machine before applying tanning material to one surface thereof. Then the skins may be reversed, slicked-out upon the other surface and additional tanning material applied to the exposed surface. It is an important characteristic of the invention that in the operations of wringing, putting-out or slicking-out, a large proportion ofthe watery content is removed from the hides or skins, the advantage being that the tanning material will penetrate into the hide or skin much more rapidly than it otherwise would.

It will be observed that the grain surface receives but one application of fresh, clean,

strong orconcentrated tanning material which may be applied by hand or by machine, employing a brush or a swab. Hence the untanned grain surface is not subjected to injury as it is from sedimentation in vats or from pins or shelves in rotating drums. Moreover, a hide or skin subjected to treatment by strong or concentrated tanning materialwhile in extended condition has its grain surface tanned to such an extent that it will not be injured during subsequent treatment to complete the tanning operation even when carried out in the usual manner in the old and well-known drum or paddle. Furthermore, because of the set given the hide or skin by partially tanning it while in extended condition, it will not shrink to any great extent in drumming to finish the tanning. This is in marked contrast to the very considerable shrinkage which accompanies the drumming of raw hides and skins introduced directly into a drum without the preliminary tanning described herein. It will 7 be seen, therefore, that certain of the advantages of the invention are retained to a large extent when the hides or skins are subjected to drumming in the process of completing the tanning.

Under certain circumstances it is preferable to permit the hide or skin to remain on the smooth supporting surface. where it receives the application of tanning material, until it dries, This treatment is applicable particularly to skins, which dry quickly in extended condition with the margins of each piece of work in as fine condition as the body portion thereof so that all portions of the tanned skin may be used to the very edge thereof. Under this treatment the skin dries with the grain surface resting on the smooth supporting surface so that the grain is not only of a fine uniform color but is smooth and of a fine quality. Since evaporation in the drying operation has taken place from the flesh surface only it is slower than when the skin is exposed to dry by evaporation from both surfaces. Hence, the tanning material has been better distributed during the drying operation, the result being that the skin is more uniformly tanned. Moreover, the skin thus tanned and dried is plumper and has a finer feeling to the sense of touch.

Where it is desired to utilize to the full capacity the supporting surfaces upon which the hides and skins are tanned, the latter may be removed, as soon as the tanning material has struck through or nearly through the individualpiece of work, or only partially through but sufiiciently to set the fibers of the hide or skin so that its extended area will be maintained in subsequent operations or treatments, and then hung up to dry in a drying chamber.

This improved method of tanning is characterized by the application of strong or concentrated tanning material directly to the grain and flesh surfaces of a raw hide or skin. This is a most important factor in securing not only a fine appearance of the finished leather but a remarkable shortening in the time required for tanning. It is found that the strong or concentrated tanning material penetrates the hide or skin, when prepared as above described, with a rapidity heretofore unheard of.

Since the hide or skin may be placed upon a supporting surface and have tanning material added in measured amounts substantially just sufficient to insure complete penetration of the hide or skin, it is clear that the amount of waste of tanning material may be reduced to a minimum. In order to avoid the necessity of calculating the amount of tanning material for each individual skin there is applied to each skin an amount slightly in excess of that required by the skin of average size in any given class of skins, thus taking care of the variation in the size of the skins of that class. Since the hide or skin is practically tanned while upon the supporting surfaces where it is spread-out in extended condition, it is clear that handling of the stock is reduced to a minimum and that there has been a real simplification of the methods heretofore employed in tanning operations.

In tanning operations upon hides, as distinguished from skins, after applying strong or concentrated tanning material alternately to the grain and flesh surfaces of the hides, it will be found necessary to make a number of additional applications of tanning material in order to supply suflicient tanning material to complete the tanning of the hides. Preferably, these repeated applications of tanning material will be made to the grain surfaces'while the hides remain stationary in extended condition upon a supporting surface. In order to eliminate the necessity of making repeatedi applioations, and particularly in the tanning of hides which may require repeated treatment over a period of six or seven days, it has been found advantageous to provide a medium for holding tanning material in contact with one or both of the surfaces of the hides, the medium being of a character to hold the tanning material in sucha Way as to permit it to pass readily to the adjacent surface of the hide. For this purpose ground cork and other similar granular substances are used as a medium for mixing with concentrated or undiluted tanning extract so that the resultant mixture may be readily spread-out in intimate contact with either or both surfaces of the hide. In certain cases, layers of fabric, such as Canton flannel, may be used in preference to the granular substance since such a fabric will not only apply the tanning material to the adjacent surface of the hide, and prevent too rapid an evaporation of the liquid part of the tanning material, but will serve also as a filter to prevent application to the grain surface of an excess of sediment should such be present in the tanning solution. In tanning with the aid of such liquid holding media as those described in accordance with the preferred manner of practising the method, the hide will first be painted with concentrated or undiluted tanning extract on the flesh surface and then placed with the flesh surface in contact with a layer of the liquid-holding medium deposited on a table or tray. Subsequently the grain side of the hide will be painted with concentrated or undiluted extract and then covered with either the granular-extract layer or with the fabric medium filled with the extract. By utilizing a medium of either of the two classes described, it is possible to apply to a hide at one operation an amount of tanning material sufficient to strike completely through the thickest hide, so that it will not require further attention on the part of the operator. At the end of six days (or even five days with thinner hides) the layers of extract-holding medium may be removed, the hide washed, and thenhung up to dry in a humidified atmosphere in a drying chamber.

In certain cases, and particularly where the extract appears to have a considerable amount of insoluble tanning material, it is desirable to wash the surfaces of the hides and skins after the first application of tanning material to the grain and flesh surfaces. This may be done by plunging the hide or skin in a body of Water or bv using a hose freely to Wash the surfaces. or skin is then promptly treated with concentrated tanning material sufficient in amount to insure striking through of the hide or skin. The advantage of this method which includes the step of washing the hide or skin becomes apparent in the shortening of the time in which the tanning materials strike through the hide or skin. This applies more particularly to the tanning of hides.

The invention and various important char- The hide acteristics thereof will now be described in detail and then pointed out more particularly in the appended claims.

In practicing the improved method of tanning hides and skins there is necessarily some variation in the method as applied to the tanning of heavy skins and hides when compared with that employed in the tanning of lighter skins, due to differences in thickness dimensions of the various classes of work. In the tanning of light skins such as sheep, kid, goat and calf, the skins are taken from the pickle or from a bath of salt solution in which they have been alloxed to remain long enough to become soft and flexible and very much of the consistency of fresh skins, the hair having been removed from the grain surface and excess flesh from the flesh surface. Upon removal from the pickle or from the salt water bath, each skin is spread out in extended condition upon a smooth supporting surface of a table or other work support. .The purpose of spreading the skin out in extended condition is to eiface all folds, creases or wrinkles particularly in the grain surface and to obtain the full area of the skin. Such spreading out may be accomplished by passing the skin first through a putting-out or slicking-out machine or by stretching it out by hand upon a smooth surface or upon a stretching frame, or by slicking-out with a hand tool. This treatment of putting-out or slicking-out expels excess liquid from the skin and spreads the skin out in smooth, firm contact with the supporting surface. In some ways the hand slick ng is preferable since the operator can slick out a skin in all directions froma central, longitudinal portion of the skin, thus stretching the skinin all directions from the central portion and thereby securing the maximum footage for that particular sk n without undue stretching of any portion thereof. While, as stated, the skin may be spread out by stretching it upon a frame or upon a smooth surface, there appears to be a real advantage in the slicking-out operation and in analogous operations such as putt ng-out and wringing since, in these operations, a very considerable amount of water is expressed from the skin at the same time that it is extended in its area. The skin which has been slicked-out appears to have empty spaces into which the tanning solution may readily enter when it is applied immediately after such treatment of the skin. The application of strong or concentrated tanning solution to the slicked-out skin is followed by rapid penetration with practically instantaneous tanning of the grain and flesh sur faces of the skin. Where the skin is shckedout by hand it is preferable to operate first upon the skin with the grain side facing upwardly in order that the first appl cation of tanning material may be to the gram side.

If the grain side receives the first application of tanning material applied in a uniform manner it will become tanned a fine uniform color that does not change during subsequent tanning operations, whereas if the grain surface be discolored in spots through the the application of tanning material inadvertently during treatment of the flesh surface no subsequent tanning can completely efface the spotted appearance of the grain surface.

After slicking the skin out upon a smooth supporting surface, a concentratedsolution of tanning material is applied to the grain surfaceeither by spraying or swabbing the tanning material uniformly over the surface, just enough of the tanning material being applied -to form a thin and substantially uniform film of tanning material on the surface. This is allowed to act on the grain surface of the skin while the same operator slicks out another skin upon an adjacent supporting surface and makes the first application of the tanning material to the grain surface of the second skin. The operator then returns to the first skin, reverses it on the supporting surface to bring the flesh surface facing upwardly. The skin is again slieked-out to the full area and concentrated tanning solution applied to such flesh surface. This second operation is then carried out on the second skin. At the completion of theoperation upon the second skin the first skin, if it be a sheep skin or kid, may be immediately removed from the table and hung up to dry in a drying chamber as will hereinafter be described.

The amount of concentrated tanning material applied successively to the two surfaces of light skins may be sufficient to strike completely through the skins. Hence, the amount of tanning material applied is carefully calculated to furnish the required amountto secure tanning of that skin without any excess to cause overtanning or waste of tanning material. In practice, a measured amount slightly more than is necessary to tan a skin of average size of a given class of skins will be applied to the skins to en sure tanning of skins which may be somewhat over the average in size, thus obviating the necessity of measuring the amount of tanning material for each skin. In accordance with this procedure seven fluid ounces of quebracho extract in solution at 120 Bkr. is applied to a sheep skin of six and one-half to seven square feet of area. In making the application it is usual to apply about onethird of the total amount to the grain side and the remainder to the flesh side since the latter takes up the tanning material more readily. A sheep skin of the size mentioned weighs, when wet, about one pound. Hence, in the tanningof sheep skins one pound of the raw skin, when wet, requires sevenflnid ounces of quebracho extract in the strength mentioned. Since hides and skins vary in thickness as well as in area and since it is the amount of collagen in a given hide or skin which must be considered in calculating the amount of tanning material, it is more accurate and useful to give the approximate amounts of tanning material in ounces per pound of raw wet hide or skin. In the case of hides, overtanning to the extent of loading hide substance with tanning material is the rule. Hence, it is necessary to use more of the quebracho extract per pound than in the tanning of skins. For this reason eight fluid ounces of quebracho extract at 120 Bkr. are applied to a hide for each pound of hide substance. It'is to be understood that in the tanning of both hides and skins tanners vary considerably in their ideas as to what constitutes a properly tanned hide or skin. Hence, while the amounts of tanning material mentioned above will give satisfactory results in the tanning of hides and skins, it is not intended in giving the estimated amount of tanning material for each pound of stock to limit the method of tanning to the application of the amount stated. Custom plays a considerable part in the decision as to whether or not a hide or skin is tanned, undertanned or overtanned. It is considered that hides and skins tanned according to methods heretofore employed are, in almost every instance, overtanned so that the limited, measured amounts for eifectingtanning of hides and skins according to this improved method are likely to be considerably less than many tanners would employ when practising the improved method herein disclosed. Further, the amount and strength of the tanning extract will vary somewhat with the different kinds of vegetable tanning extracts which are employed in the tanning of hides and skins, and with different classes of skins in accordancewith the qualities desired in the finished leather.

While the tanning material may not have .struck completely through the skin at the time that it is removed from the table, the grain and flesh surfaces of the skin have been instantaneously tanned by the application of the strong tanning material and the fibers of the skin have been given such a set, during the time allowed, that the skin will maintain throughout all subsequent operations of this improved method the full area of the slicked-out skin. Hence there is no objection to lifting this skin from the'supporting surdrying room, since it will not shrink in area during the drying operation. If the atmospherein thedrying roombe humidified to prevent too rapid drying, it has been found that time is given for the tanning solution to penetrate uniformly throughout the skin so that the latter dries thoroughly tanned through in all its parts and with a clear uniform color.

face and hanging it up immediately in the The drying room should preferably be dark since excess of light, whether direct or refiected, is apt to darken the surface of the leather. It isremarkable how rapidly the skins dry in the drying room inspite of the presence of humidified atmosphere which tends to lessen the rapidity of the action. The rapid drying is due, in large measure, however, to the fact that, in tanning in accordance with the improved method, such limited amounts of tanning solutions are employed (of which the tanning material itself constitutes a high percentage) that relatively small amounts of water remain to be dispersed in the drying operation. This situation is in strong contrast to that which ob,- tains in the tanning of skins in drums or vats since, in the latter case, the skins (now in the form of leather) come, from the vats dripping wet and full of water. Even though they are subsequently slicked-out before drying, there are relatively great amounts of water to be got rid of in the drying operation. I

While it is an advantage to be able to take the skins from the supports soon after they have received applications of tanning material and hang them up to dry in a drying chamber, since the supports whether they be tables or stretching frame or other supports are thus made available for use with fresh pieces of work, there are other advantages in permitting the skins to dry upon smooth work supporting surfaces, preferably in place upon the surfaces where they received the applications of tanning material, and these advantages may offset the advantage of being able to utilize the supporting surfaces for fresh pieces of work after very short intervals.

Among these advantages ma be mentioned the fact that a skin allowed to dry upon the smooth surface where it received the application of tanning material, not only maintains its full slicked-out area but the margins of the skin as well as the body portion thereof dry absolutely fiat and smooth, whereas there is a tendency for the margins of the skin to curl somewhat when the skin is hung up to dry in the drying chamber. When the skin is allowed to dry on a smooth supporting surface, such as that afforded by a glass orbrass plate, it is preferably with the grain side down, the purpose being to secure a fine, lossy grain surface which is, moreover, very ight in color largely for the reason that it has been protected from light and from oxidation in the atmosphere. Furthermore, the skin thus treated appears to dry more uniformly, apparently because it remains damp long enough (evaporation taking place 7 from the-flesh surface only) for the tanning material to be evenly distributed to even agreater degree than when the skin is suspended in the drying chamber. At any rate, the quality of the skin is finer than a correis, while tanning material is being applied to the exposedsurface. It is believed that a cer-' tain amount of evaporation takes place from the exposed surface to which tanning material has been applied so that as the surface of the leather takes up the tanning material from the film or layer of tanning material applied 'thereto thus reducing the strength of the solution, evaporation helps to keep up the strength of the thin layer of tanning substance. In accordance with this method the skin is stationary while being tanned, thus avoiding danger of injury to the skin and particularly to the delicate grain surface of untanned hides or skins, such as frequently takes place in drum tanning so universally practised heretofore.

lVhile a sheep or kid skin will have suficient tanning material applied to it to effect complete tanning-of the skin in making a single application to each surface, that is, to the grain and to the flesh surface, it may require a second or even a third application ofstronger or concentrated tanning material to the flesh surface in order to supply sufficient tanning material to effect complete penetration of the skin when the latter is a goat or a calf skin of the heavier grades. Otherwisethe steps are the same as with the lightest sheep or kid. One of the marked advan: tages of the method resides in the application of just the right amount of tanning material to effect tanning without any substantial waste. This, as heretofore pointed out, is in marked contrast to the tremendous quantities of tanning solutions ordinarily provide for the tanning of hides and skins, much of which is wasted through being discharged into the sewer. The most important feature, however, of the improved tanning method resides in the fact that the application of tanning material suflicient to tan the skins is effected within a few minutes and the penetration of the concentrated tanning material is so extraordinarily rapid that the skin may be completely tanned without further attention on the part of the operator. It has been found that drying of the skin in a humidified atmosphere, whether suspended from bars or spread out on a flat surface, secures uniform distribution of the tanning material and that the drying of the skin thus treated effects completion of the tanning, that is, a union of the tannin with the collagen of the fibers under conditions which favor oxidation of the tannin or of the combined tannin and collagen, whereby the union of the tannin and collagen is unusually well fixed.

A matter of the utmost importance in the improved method is that tanning material of high concentration, and even theundiluted extract, may be applied, in accordance with this method, directly to the grain and to the flesh surfaces of the raw hide or skin. Any tanner not acquainted with the experimental work performed in developing this process would regard the application of concentrated tanning material to a raw hide or skin as certain to produce case-hardening of the surfaces of the hide or skin together with destructive shrinking of the hide or skin and a drawn or wrinkled grain surface, due to the action of the concentrated tanning solution. I have discovered that, on the contrary, undiluted tanning extract, so heavy that it resembles syrup, may be applied, under the conditions herein disclosed, directly to the grain surface of the hide or skin without in ury. While a tanning extract in a solution in excess of 140 Bkr. may be employed in the first application of tanning material to the raw hide or skin, I have found it advantageous to employ solutions of various tanning materials at a strength of from 100 to 120 Bkr., since the action is sufficiently rapid in the tanning of light skins, which must be manipulated more or less by the operator in the stretching and tanning operations. Under certain conditions, it may be desirable to apply stronger solutions than 120 to the flesh surface to hasten the tanning operation, while continuing to use solutions of 120 or less on the grain surface. The advantages of using such strong solutions from the .very beginnin are several, among which may be specific the fact that the surfaces of the hide or skin'are practically instantaneously tanned so that a hide or skin spread out in extended condition becomes, in an extremely short time, so set in this extended condition that it will not subsequently shrink but will maintain its extended area throughout the tanning operation carried out in accordance with this method.

. Apparently, the strong or'concentrated tanning solution penetrates so quickly and to a suflicient depth in a few-minutes that a suflicient quantity of the fibers of each surface of the hide or skin become so set in their extended condition as to hold the hide or skin against shrinking, whereby its extended area is maintained. When it is understood that all light leathers are sold by the foot it will be realized that, to the tanner, the matter of securing the maximum area consistent with the desired quality from his hides and skins is a matter of the greatest importance. It is a fact, however, that all skins shrink considerably in area when tanned according to commonly practiced methods, particularly if they are drummed in the tanning operations,'thus making necessary other operations in an attempt to make up the loss in area. In contrast to this, there is secured by this improved method the maintenance of area by spreading the skin out in its normal area before any tanning is attempted, and then effecting the tanning operation in such a way as to maintain the extended area. Another advantage of applying the strong or concentrated tanning solution to a hide or skin and, particularly to the light skins, is that following the application of such tanning solutions the skins may be immediately allowed to dry since the fibers in both surfaces of the skins have been so set in this partial tanning operation that they will not permit shrinking of the skin while it is drying in the desired humidified atmosphere. Further, the quantity of tanning solution required for each hide or skin is so small that it may be easily handled with a minimum of effort on the part of the operator and readily controlled so that just the right amount may be readily distributed in a uniform manner over the surfaces of the hides or skins to be treated. Another advantage of the limited amount of tanning solution applied to each hide or skin is that by this method both the grain and the flesh surfaces are kept clean. In other words, there are no large amounts of sediments to collect upon the surfaces of the hides or skins and no foul and slimy tanning liquors to act injuriously upon the surfaces since the liquor applied, according to the improved method, is a new, clean, and concentrated product. While, according to the improved method, it is proposed to use concentrated tanning solutions, that is, solutions not substantially less than 100 Bkr. in strength, it is to be understood that the method is not limited to the use of such concentrated solutions, since it has been demonstrated by experimentation that application of strong tanning solutions directly to the raw hide or skin secures advantageous results never before obtained, although not so rapidly as when concentrated solutions are employed. By a strong solution is meant a solution of substantiall greater strength than the solutions common y applied directly to a raw hide or skin. Hides and skins have been tanned successfully bythe method herein described uped to secure the application of tanning material simultaneously to both sides of the hide or skin, provided that the hide or skin thus treated be promptly spread-out, preferably by slicking-out upon a smooth surface, before the fibersin and near the surfaces of the hide or skin commence to set in their then unstretched or unextended condition. In other words while it is preferable to place the skin in an extended condition before applying tanning material these steps may be reversed, provided that the hide or skin is slicked-out or stretched-out promptly enough after the application of the tanning material.

lit

As a result of the application of a concentrated tanning solution to both surfaces of skins of various classes, partial or complete tanning of the skins takes place. Even if the amount of tanning material applied in a single application to the grain and the flesh surfaces be not sufiicient to strike completely through the skin the latter is preserved from putrefactive changes. Skins thus treated may be piled and left in a moist condition for lengthy periods of time, weeks or months even, before completing the tanning operation. 011 the other hand, skins treated as above described may be dried by suspending them in the atmosphere. Even though they be incompletely tanned they will keep indefinitely in dry rooms under ordinary atmospheric conditions. These skins I may subsequently be thoroughly moistened With water, since they will wet back readily, and the tanning operation completed either by the method herein disclosed or by methods heretofore practised in the tanning of skins The important facts to be noted in connection with the treatment of raw skins with concentrated tanning material is that the'skins are preserved in their fully extended condition, that the grain surfaces of the skins are tanned a fine uniform color which will not subsequently change, that the grain surfaces are not susceptible to injury except upon unusually harsh treatment, and that the com pletion of the tanning operation may be carried out either in the same factory in accordance with the method herein disclosed or in any other factory and by methods long en1 ployed in the tanning industry.

The foregoing description of the method applies to all skins and even to splits from heavy hides, which may be readily placed in extended condition either upon a smooth surface or upon a frame. Some modification, however, is necessary in the tanning of hides intended for sole leather, belting, and other heavy leathers. These hides may be simply placed in extended condition upon support-. ing surfaces without attempt to stretch them for the purpose of increasing the area, since leather from hides is sold by the pound and not by the foot and since the weight and face to such an extent as to efiace all folds,

creases or wrinkles, it is treated, preferably upon the flesh surface first, with a-strong or concentrated tanning solution and is then placed upon a liquid containing medium in a tray with the flesh surface down. N ext the grain surface is treated with the strong or concentrated tanning solution. The reason for treating the flesh surfaces first in the case of hides is that it would be extremely difi'lcult to avoid wrinkling the grain surface in turning the heavy hide over to get at the flesh surface. If such wrinkling occurred in a freshly tanned grain surface the wrinkles would be permanent or removable only with difiiculty. Hence, the grain should be treated after the hide has been spread out in condition to stay until struck through with tanning material. Since the hide is of considerable thickness it will re quire the application of tanning material periodically over a longer time than is required for a skin. Hence, it is preferred to employ some medium for holding the tanning solution in contact with the surface of the hide. For this purpose coarse wood-dust or oatmeal may be employed, saturated with the tanning solution in the bottom of a shallow pan or other receptacle of a size to contain a full sized hide, if desired, it being understood that the hide may be previously cut up into pieces of a predetermined size and shape according to the uses to which the various portions will naturally be put. For holding, the tanning solution in Contact with the upper surface of the hide undergoing treatment it is convenient to use the liquid holding substances mentioned above or a fabric, such as Canton flannel, soaked with the tanning solution and spread over the surface of the hide. A layer of fabric acts also as a filter to prevent sediment from accumulating on the subadjacent surface of the hide. In adding further amounts of the tanning material, it may simply be poured upon the'liquid-holding medium and spread out so as to be substantially uniform over the whole surface.- The hide is stationaryvin a horizontal position throughout the whole time of its treatment, which takes about six days for hides of medium thickness. Lighter hides may take only five days while heavier ones may take a slightly longer time.

It has been found in the tanning of hides that even more concentrated tanning solutions may be used advantageously than in the tanning of skinslargely because of the consequent reduction in the time required for completing the penetration of the hide. Highly concentrated or even undiluted tanning extract may be mixed with ground cork or other similar granular material or with other liquid holding material, which does not itself absorb the tanning material, such, for instance, as waste wool, usually referred to as noils. The mixture of cork or of noils with concentrated tanning extract may be utilized in applying the tanning material to one or both sides of the hide. Preferably, the hide wil be swabbed or sprayed on its flesh surface with concentrated tanning extract and then placed upon a layer of the liquid holding medium filled with tanning material and spread out upona table or tray. After the hide has been spread out in the manner indicated, the grain surface is treated with the concentrated extract and then a layer of the liquor holding medium is spread over the grain surface in a quantity suflicient, when taken in conjunction with the quantity below the flesh surface of the hide, to insure the provision of sufficient tanning material to strike completely through the hide. In this case the quantity of tanning material applied to the surfaces of the hide is in excess of that required for complete tanning in order to insure complete penetration by the tanning material without further attention on the part of the operator. At the end of five or six days, according to the thickness of the hide, it will be found completely struck through. The mixture of tanning material and cork or noils may be then wiped from the surface of the hide or the layer of fabric removed from the hide, the latter washed to remove excess tanning material from the surfaces and then hung up to dry in the drying chamber. It will be observed that in this method of tanning the hide the application of tanning material is made complete by the swabbing or spraying of tanning material alternately upon the flesh and grain surfaces of the hide and then by bringing the mixture of cork or noils with tanning material, or a layer of fabric filled with tanning material, into contact with both surfaces of the hide and that thereafter no further attention is required until the end of the fifth or sixth day when the hide will be found struck through with tanning material.

When a hide has been completely struck through as a result of the application of the required amount of tanning material, it is removed from the table or tray washed and then hung up to dry in the drying room. The time necessary for drying is reduced to a remarkable extent as compared with the ten days or two weeks time which in the past has been necessary to effect the drying of hides. Because of the limited amount of concentrated tanning solution utilized in the tanning of the hide there is very little water to be removed in the drying room so that drying rarely takes more than three days, even for the thickest hides.

In certain cases, as for instance, where the tanning material is partly in suspension as well as in solution, it is distinctly advantageous to wash the .hide or the skin after the first application of the strong or concentrated tanning solution. This washing may be effected by sousing the work in a body of water or by using a hose for a brief period. After this operation the hide or skin is at once spread out again and another application of the strong or concentrated tanning solution made and the treatment continued as before. In some cases the step of washing the hide or skin has produced such excellent results in speeding up the time required for tanning that it is considered an important step in the method under such circumstances.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. That improvement in methods of tanning hides and skins which comprises stretching a hide or skin out in fully extended condition on a supporting surface, and alternately treating the grain and flesh surfaces of said hide. or skin while in such extended condition on said supporting surface with a tanning material in a limited amount sufficient completely to penetrate the hide or skin.

2. That improvement in methods of tanning hides and skins which comprises stretching a hide or skin out in fully extended condition on a smooth supporting surface, treating both surfaces of the hide or skin while in such extended condition with a strong tanning solution of an amount to provide a substantial film of the tanning solution on both surfaces of the hide or skin, and subsequently subjecting the hide or skin to further treatment by tanning material to effect completion of the tanning operation.

3. That improvement in methods of tanning hides and skins which comprises stretching a hide or skin out in fully extended condition on a supporting surface, applyinga strong solution of tanning material in an amount to cover thinly both surfaces of the raw hide or skin while in such extended condition on the supporting surface, to secure a clear uniform color, particularly of the grain surface, and to effect a partial tanning of both surfaces, and subsequently subjecting the hide or skin to treatment by a strong or concentrated tanning solution sufiicient in amount to complete the tanning of the hide or skin.

4. That improvement in methods of tanning hides and skins which comprises stretching a hide or skin out in fully extended condition on a supporting surface with one surface of the hide or skin exposed to the atmosphere, and applying a solution of tanning material to the exposed surface in a quantity suflicient to effect complete penetration of the hide or skin by the, tanning material.

5. That improvement in methods of tanning hides and skins which comprises placing a hide or skin in extended condition on a supporting surface with one surface of the.

hide or skin exposed to the atmosphere, applying a limited amount of a strong solution of tanningmaterial to the hide or skin, and repeating the application of such limited amount while the hide or skin remains in extended condition on the supporting surface and until it is completely penetrated by the tanning material.

6. That improvement in methods of tanning hides and skins which comprises stretching a raw hide or skin out in fully extended condition on a supporting surface, and applying to the raw hide or skin a solution of tanning material of substantially not less than 100 Bkr. in a quantity sufiicient to effect complete penetration of the hide or skin by such tanning solution.

7. That improvement in methods of tanning hides and skins which comprises supporting a hide or skin in extended condition with at least one surface exposed to the atmo'sphere,treating the hide or skin while in extended condition with a tan-- ning solution of-an amount to provide a substantial film of the tanning solution on the exposed surface of the hide or skin so that reduction in the strength of the solution due to absorption by the hide or skin is balanced to a degree by evaporation in the atmosphere, and repeating the application of the tanning solution until the hide or skin is completely struck through.

8. That improvement in methods of tanning hides and skins which comprises supporting a hide or skin in extended condition with at least one surface exposed to the atmosphere, and treating the hide or skin while 7 stationary in extended condition with a tanning material sufficient in amount completely to penetrate the hide or skin.

9. That improvement in methods of tanning hides and skins which comprises supporting a hide or skin in extended condition with at least one surface exposed to the at mosphere, treating the hide or skin while in extended condition with a concentrated tanning solution of an amount to provide a relatively thin layer of the concentrated tanning solution on the exposed surface of the hide or skin, and then applying concentrated tanning solution to the other side of the hide or skin in an amount suflicient, in conjunction with that applied in a thin layer, to penetrate completely through the hide or skin.

10. That improvement in methods of tannin g hides or skins which comprises stretching a hide or skin out in extended condition With at least one surface exposed to the atmosphere, to both surfaces of the hide or skin while stationary in extended condition in an amountjust suflicient to penetrate completely through the hide or skin.

11. That improvement in methods of tanning hides and'skins which com rises stretching a raw hide or skin out-in. ully extended condition, and applying a concentrated solution of tanning material to the raw hide or skin in a quantity just sufficient to effect complete penetration of the hide or skin by the tanning material.

12. That improvement in methods of tanning hides and skins which comprises stretching a raw hide or skin out in fully extended condition, applying a limited amount of a concentrated solution of tanning material to the raw hide or skin, and repeating the application of such limited amount until sufiicient tanning material has been applied to penetrate the hide or skin completely.

13. That improvement in methods of tanning hides and skins which comprise stretching a raw hide or skin out in fully extended condition, applying a limited amount of a strong or concentrated solution of tanning material to the grain surface of the raw hide or skin to effect tanning of the grain surface, and then subjecting the hide or skin to treatment by strong or concentrated tanning material to complete the tanning thereof.-

14. That improvement in methods of tan- .ning hides and skins which comprises placing a raw hide or skin on a supporting surface, slicking the hide or skin out in extended condition on the supporting surface, and applying a strong solution of tanning material to both surfaces in turn in a quantity sufficient to effect complete penetration of the hide or skin by the tanning solution.

15. That improvement in methods of tanning hides and skins which comprises placing a raw hide or skin on a supporting surface, slicking the hide or skin out in extended condition on the supporting surface, applying a strong solution of tanning material to both surfaces in turn in a quantity suflicient to ef fect complete penetration of the hide or skin by the tanning solution, and permitting the hide or skin to dry in its slicked out condition on the supporting surface.

16. That improvement in methods of tanning hides and skins which comprises slick-' ing a raw hide or skin out in extended condition upon a smooth surface, applying to the raw hide or skin a solution of tanning material of substantially not less than 100 Bkr. in a quantity suflicient to efi'ect complete penetration of the hideor skin by such tanning solution, and then permitting the treated hide or skin to dry while in its slicked-out condition on the smooth supporting surface.

17 That improvement in methods of tanning hides and skins which comprises placand applying a tanning material ing a raw hide or skin on a supporting surface, slicking the hide or skin out in extended condition on the surface, and applying a strong solution of tanning material to both surfaces in turn in a quantity to effect complete penetration of the hide or skin by the tanning solution, and then permitting the hide or skin to dry on the supporting surface in position in which the last application of tannin material was made.-

18. That improvement in methods of tanning hides and skins which comprises placing a raw hide or skin on a smooth supporting surface, slicking the hide or skin out in the extended condition on the supporting surface, applying a strong solution of tanning material to the exposed surface of the hide or skin, reversing the hide or skin, slicking it out a second time to expose the untreated surface in stretched out condition, and then applying strong tanning solution in a quantity to effect complete penetration of the hide or skin by the tanning solution.

19. That improvement in methods of tanning hides and skins which comprises stretching a raw hide or skin out in fully extended condition on a smooth surface, applying to the raw hide or skin a concentrated tanning material to effect instantaneous tanning of the surfaces of the hide or skin, the tannin material being applied in an amount su cient to strike through the hide or skin, and then drying the hide or skin in a humidified atmosphere to secure even distribution of the tanning material.

20. That improvement in methods of tanning hidesand skins which comprises placing a hide or skin in extended condition on a supporting surface, applying a strong solution of tanning material in a measured quantity slightly more than sufficient to insure complete penetration of the hide or skin by the tanning solution, and permitting the hide or skin to dry while in extended condition on a supporting surface.

21. That improvement in methods of tanning hides and skins which comprises placing a hide or skin in extended condition on a supporting surface, applying to the raw hide or skin a strong solution of tanning material in a quantity sufiicient to effect complete penetration of the hide or skin by the tanning solution, and suspending the hide or skin in a humidified atmosphere to dry slowly and thus secure even distribution of the tanning materi a1.

22. That improvement in methods of tanning hides and skins which comprises placing a hide or skin in extended condition on a supporting surface, applying to the raw hide or skin a strong solution of tanning material in a quantity sufficient to effect complete penetration of the hide or skin by the tanning solution, and suspending the hide or skin in a darkened chamber and in a humidified atmosphere to dry slowly Without access of light.

23. That improvement in methods of tanning hides and skins which comprises supporting a raw hide or skin in extended condition with at least one surface exposed to the atmosphere, applying a concentrated solution of tanning material to said exposed surface of the raw hide or skin in a quantity sufficient to effect complete penetration of the hide or skin by the tanning material, and then permitting the hide or skin to dry.

24. That improvement in methods of tanning hides and skins vwhich comprises supporting a raw hide or skin in extended condition, applying to the raw hide or skin a solution of tanning material of substantially not less than 100 Bkr. in a quantity sufiicient to effect complete penetration of the hide or skin by such tanning solution, and then drying the treated hide or skin in a humidified atmosphere.

25. That improvement in methods of tanning hides and skins which comprises supporting a hide or skin in extended condition, applying tanning material to both sides of a hide or skin while in extended condition, permitting the tanning material to act on the extended hide or skin for a certain time to secure the setting of the hide or skin in extended condition, and then subjecting the hide or skin to treatment by a strong tanning material in a quantity sufficient to strike completely through the hide or skin.

26. That improvement in methods of tanning hides and skins which comprises stretching a raw hide or skin and holding it in extended condition, applying a limited amount of strong solution of tanning material alternately to both surfaces of the hide or skin to effect a partial tanning of the hide or skin whereby it subsequently maintains its extended area, and then repeating the application of the strong solution of tanning material until sufiicient tanning material has been applied to penetrate the hide or skin.

27. That improvement in methods of tanning hides and skins which comprises placing a raw hide or skin on a supporting surface, slicking the hide or skin out in extended condition on the supporting surface, applying to the raw hide or skin a concentrated tanning material to effect instantaneous tanning of the surfaces of the hide or skin whereby it will subsequently maintain its slicked-out area, and then repeating the application of tanning material.

28. That improvement in methods of tanning hides and skins which comprises stretching a hide or skin out in fully extended condition on a supporting surface, treating the raw hide or skin with a concentrated tanning solution applied alternately to both surfaces of the hide or skin while on said supporting surface until the tanning material has comill nsenese pletely penetrated the hide or skin, and minunizmg access of light until tanning is complete.

29. That improvement in methods of.

tanning hides and skins which comprises stretching a raw hide or skin out in fully extended condition, applying to the raw hide or skin while in stretched condition a thin layer of solution of tanning material to efiect a partial tanning of the surfaces of the hide or skin while it is in fully extended condition whereby it will subsequently maintain its extended area, repeating the application of tanning material until the hide or skin is struck through, and then permitting the hide or skin to dry while in extended condition.

30. That improvement in methods of tanning hides and skins which comprises eflecting instantaneous tanning of both surfaces of the hide or skin while supported in extended condition by applying a concentrated solution of the tanning material-to the raw surfaces of the hide or skin, theamount of the concentrated tanning solution applied being limited but sufficient to penetrate completely through the hide or skin, and then exposing one surface only of the hide or skin to the atmosphere to dry and thereby complete tanning of the hide or skin.

31. That improvement in methods of tanning hides and skins which comprises applying a substantial film of liquid tanning material to both surfaces of a raw hide or skin while in fully extended condition to efiect substantially instantaneous tanning of those surfaces, subsequently applying strong tanning material in an amount suiiicient completely to tan the hide or skin, and then drying the hide or-skin slowlyto secure even distribution-of the tanning material.

32. That improvement in methods of tanning hides and skins which comprises applying a substantial film of liquid tanning material to both surfaces of a 'raw hide or skin while at rest in fully extended condition to efi'ect substantially instantaneous tanning of those surfaces and subsequent complete penetration of the hide or skin by the tanning material, and then exposing the hide or skin to the atmosphere to dry the same.

33. That improvement in methods of tanning hides and skins which com rises placing a hide or skin in extended con ition on a supporting surface, treating the hide or skin with a tanning solution while on said supporting surface and until the tanning material has completely penetrated the hide or skin, and providing for evaporation of the tanning solution from one of the surfaces of the hide or skin during tanning thereof.

34. That improvement in methods of tanning hides and skins which comprises supporting a raw hide or skin in extended condition, treating the raw hide or skin with a concentrated tanning solution in a measured quantity just sufiicient completely to penetrate the hide or skin, and providing for evaporation of the tanning solution from the surfaces of'the hide or skin.

35. That improvement in methods of tanning hides and skins which comprises effecting practically instantaneous tanning of both surfaces of the hide or skin while spread out-in extended condition by applying a strong solution of the tanning material to the raw surfaces of the hide or skin and after the application of tanning material maintaining the hide or skin in fully extended condition for a time sufficient to secure setting of the hide or skin in such extended condition, and subsequently completing the tannage of the hide or skin by subjecting it to treatment by further sufiicient amounts of strong or concentrated tanning solution.-

36. That improvement in methods of tanning hides and skins which comprises applying a substantial film of liquid tanning material to both surfaces of a raw hide or skin to effect substantially instantaneous tanning of those surfaces, and then drying the hide or skin slowly.

37. That improvement in methods of tanning hides and skins whichcomprises applying a substantial film of strong or concentrated liquid tanning material to both surfaces of a raw hide or skin to effect substantially instantaneous tanning of those surfaces, and subsequently applying strong tanning material in measured amount just sufficient to complete the tanning of the hide or skin.

38. That improvement in methods of tanning hides and skins which comprises supplying a medium with a substantial layer of a concentrated solution of a tanning materlal, placing a raw hide or skin in extended condltion'upon said holding medium and in contact with the layer of concentrated tanning material so that the tanning material may act upon the lower surface of the hide or skin, applying concentrated tanning material to the upper surface of the hide or skin in a quantity suificient to secure in conjunction with the layer of tanning material below the hide or skin complete penetration thereof by the tanning material, sembled hide or skin and material-holding medium to the atmosphere.

39. That improvement in methods of tanning hides and skins which comprises placing upon a support a layer of fabric adapted to hold a substantial amount of tanning material interpenetrating the fabric, applying tanning material to the fabric, placing a hide or skin in extended condition upon said fabric and in contact with the layer of tanning solution so that the tanning material may diffuse upwardly into the hide or skin, applying tanning'solution to the upper surface of the hide or skin in a quantity suflicient to and exposing the assecure in conjunction with the layer of tanning solution below the hide or skin complete penetration thereof by the tanning material, and subjecting the treated hide or skin and layer of fabric to the action of the atmosphere.

40. That improvement in methods of tanning hides and skins which comprises placing upon a supporting surface a liquid holding medium for holding a substantial amount of tanning material interpenetrating the medium, applying tanning material to the medium, applying tannin material to the flesh surface of a hide or stin, then placing the hide or skin flesh surface down upon the layer of holding medium, and applying tanning material to the grain surface in a quantity sufficient to secure in conjunction with the layer of tanning material below the flesh slqrface complete penetration of the hide or s in.

41. That improvement in methods of tanning hides and skins which comprises placing upon a supporting surface a liquid holding medium for holding a substantial layer of concentrated tanning solution, applying tanning material to the medium either before or after placing it on the supporting surface, lacing a raw hide or skin upon said liquid iolding medium and in extended condition in contact with the layer of concentrated tanning solution so that the tanning material may diffuse upwardly into the hide or skin, applying a substantial film of concentrated tanning solution to the upper surface of the hide or skin, placing over such upper surface a layer of material interpenetrated with concentrated tannin solution, and providing for evaporation of the water in the tanning material a plied to the hide or skin.

42. '1 at improvement in methods of tanning hides and skins which comprises placing upon a supporting surface a liquid holding medium for holding a substantial layer of tanning solution, applying tanning material to the medium either before or after placing it on the supporting surface, placing a hide or skin upon said liquid holding medium and in contact with the layer of tanning solution so that the tanning material may diffuse upwardly into the hide or skin, applying a substantial film of concentrated tanning solution to the top surface of the hide or skin, superimposing upon said surface a layer of material, keeping the layer moist with a'concentrated tanning solution, and providing for evaporation of water in the tanning material applied to the top layer of material.

43. That improvement in methods of tan- 7 ning raw hides and skins which comprises supplying a liquid-holding medium with a su stantial quantity of concentrated tanning material, and bringing the holding medium filled with concentrated tanning material and 5 the raw hide or skin together exposed to the atmosphere with the holding medium held in intimate contact over both surfaces of the hide or skin until the hide or skin is struck through.

44. That improvement in methods of tanning raw hides and skins which comprises supplying a liquid-holding medium with a substantial quantity of tanning material, bringing the holding medium filled with tanning material and the hide or skin into intimate contact upon the flesh surface of the hide or skin, applying a substantial amount of tanning material to the grain surface of the hide or skin, and exposing the treated grain surface to the action of the atmosphere.

45. That improvement in methods of tanning raw hides and skins which comprises supplying a liquid holding medium with a quantity of tanning solution, bringing the liquid-holding medium interpenetrated with tanning solution and the hide or skin together exposed to the atmosphere with the holding medium held in intimate contact over both surfaces of the hide or skin, and adding tanning solution to the medium to furnish a quantity of tanning solution sufiicient to tan the hide or skin.

elf}. That improvement in methods of tanning raw hides and skins which comprises supplying a liquid-holding material with a substantial layer of tanning solution, placing a hide or skin upon said holding material filled with tanning solution in intimate contact therewith so that the tanning solution may difi'use upwardly into the hide or skin, applying a substantial film of concentrated tanning material to the upper surface of the raw hide or skin, superimposing upon said upper surface an absorptive layer of material, and adding concentrated tanning solution periodically to the absorptive layer in predetermined amount substantially just suflicient to secure complete tanning of the hide or skin.

47. That improvement in methods of tanning raw hides and skins which comprises applying a concentrated tanning solution to both surfaces of a hide or skin, applying an absorptive filtering layer of material to the grain surface of the hide or skin, and periodically adding concentrated tanning solution to the absorptive filtering layer so that the tanning solution reaches the juxtaposed grain surface of the hide or skin through the said absorptive filtering layer of material.

48. That improvement in methods of tanning hides and skins which comprises placing a raw hide or skin on a supporting surface, slicking the hide or skin out in extended condition on the supporting surface, applying tanning material to both surfaces of the slicked-out hide or skin to tan the surfaces of the hide or skin and give such a set to the fibers that the hide or skin will maintain the area secured in the slicking operation, then washing the hide or skin thus treated, and

nausea:

applying strong tanning solution to the hide or skin in a quantity suf'ficientto efi'ect complete penetration of the hide or skin by the tanning solution.

49. The improvement in methods of tanning hides and skins which comprises placing a raw hideor skin on a supporting surface, stretching the hide or skin out in extended condition on the supporting surface, applying strong tanning material to both surfaces of the hide or skin in turn to efi'ect practically instantaneous tanning of the surfaces of the hide or skin and give such a set to the fibers that the hide or skin will maintain the area secured in the stretching operation, then washing the hide or skin thus treated, and applying tannin material to the hide or skin in a quantity su cient to efi'ect complete penetration of the hide or skin by the tanning material. v

50. That improvement in methods of tanning hides and skins which comprises stretching a raw hide or skin and holding it in extended condition, applying to the raw hide or skin while in extended condition tanning material to efiect substantially instantaneous tanning of the surfaces of the hide or skin.

whereby it will subsequently maintain its extended area, then washing the hide or skin thus treated, and repeating the application of tanning material with a quantity sufiicient completely to penetrate the hide or skin.

51. That improvement in methods of tanning hides and skins which comprises sup-' porting a raw hide or skin in extended condition, applying to the raw hide or skin a concentrated tanning material to effect practically instantaneous tanning of the surfaces of the hide or skin, then washing the hide or skin thus treated, and repeating the application of tanning material with a quantity suflicient completely to penetrate the hide or skin.

52. That improvement in methods of eitning hides and skins which comprises, ap-

plying asubstantial film of a tanning solution not substantially lower than 100 Bkr. to both surfaces of a hide or skin in rapid succession to effect substantial instantaneous tanning of both surfaces of the hide or skin while supported in extended condition, then washing the hide or skin thus treated, and subsequently applying further amounts of strong tanning solution sufficient to effect complete tanning of the hide or skin.

53. That improvement in methods of tanning hides and skins which comprises applying a strong tanning solution to the grain surface of a hide or skin and a much stronger or concentrated solution to the flesh surface thereof.

' 54. That improvement in methods of tanning hides and skins which comprises stretch- I ing a hide or skin out in fully extendedconditon, applying tanning material to the fully extended hide or skin in an amount sufficient to efl'ect tanning thereof, and maintaining the hide or skin in fully extended condition during and after the application of tanning material until the hide or skin has set in its fully extended condition.

55. That improvement in methods of -tan- 56. That improvement in methods of tanning hides and skins which comprises stretching a hide or skin out infully extended condition, applying tanning material to the fully extended hide or skin and maintaining the hide or skin in fully extended condition during and after the application of tanning material until the hide or skin has set in its fully extended condition, and subsequently subjecting the hide or skin to treatment to com plete the tanning thereof. 5

57. That improvement in methods of tanning hides and skins which comprises stretching a hide or skin out in fully extended condition on a smooth supporting surface, subjecting the hide or skin while thus stretchd out to treatment by tanning material, main; taining the hide or skin in such extended condition during and after the treatment by tanning material until the hide or skin has set in such extended condition, and subsequently completing the tanning of the hide or skin by further treatment with tanning material.

58. That improvement in methods of tanning hides and skins which comprises slicking a raw hide or skin out in extended condition upon a smooth surface, applying to the raw hide or skin a solution of tanning material of substantially not less than Bkr. in a restricted amount to effect tanning of the grain surface of the hide or skin by such tanning solution, and subsequently subjecting the hide or skin to treatment by a strong or concentrated tanning solution to complete the V tanning thereof.

59. That improvement in methods of tanning hides and skinswhich comprises stretch- .ing a raw hide or skin and holding it in extended condition,.applying a limited amount of strong solution of tanmng material alternately to both surfaces of the hide or skin toefiect a partial tanning of the hide or skin whereby it subsequently maintains its extended area,- and then subjecting the hide or skin to a strong or concentrated solution of tanning material until it is completely tanned.

60. That improvement in methods of tanning hides and skins which eomprises spreading a hide or skin out in fully extended content from a hide or s in, stretching the hide or skin out in fully extended condition, and

subjecting the hide or skin while in stretched condition to treatment by strong or concentrated tanning material, in an amount sufficient to efi'ect tanning of both surfaces thereof, until the hide or skin has set in such extended condition.

62. That improvement in methods of tanning hides and skins which comprises slicking a hide or skin out in fully extended condition upon a supporting surface and simultaneously therewith removing a substantial pro ortion of the water content of the hide or s 'n, and subjecting the hide or skin while in a fully extended condition to treatment by strong or concentrated tanning material, in an amount suflicient to effect complete tanning thereof, until the hide or skin has set in such fully extended condition.

63. That improvement in methods of mm ning hides and skins which comprises slicking a hide or skin out in fully extended condition upon a smooth supporting surface and simultaneously therewith removing the greater portion of the water content of the hide or skin, applying a strong or concentrated tanning material to the hide or skin while in fully extended condition in an amount suflicient to efiect complete tanning thereof, and maintaining the hide or skin in such fully extended condition until it has been set in such extended condition by the tanning material, and subsequently treating the hide or skin with tanning material to complete the tanning operation.

64. That improvement in methods of tanning hides and skins which comprises spreading a hide or skin out in fully extended condition and simultaneously therewith removing a large proportion of the water from the hide or skin, applying a strong or concentrated tanning solution to the fully extended hide or skin, maintaining the hide or skin in fully extended condition during and after the application of the tanning material until the hide or skin has set in its fully extended condition, and then completing the tanning operation of the hide or skin by further treatment with tanning material. l

65. That improvement in methods of tanning hides and skins which comprises re moving a substantial quantity of the water content from a hide or skin, stretching the hide or skin out in full extended condition, subjecting the hide or skin while in stretched condition to treatment by strong or concentrated tanning material until the hide or skin has set in such extended condition, and subsequently completing the tanning of the hide or skin by further treatment with strong or concentrated tanning material.

66. That improvement in methods of tanning hides and skins which comprises slicking a hide or skin out in fully extended condition upon a supporting surface and simultaneously therewith removing a substantial proportion of the water content of the hide or skin, subjecting the hide or skin while in a fully extended condition to treatment by strong or concentrated tanning material until the hide. or skin has set in such 'fully extended condition, and subsequently treating the hide or skin with a suflicient amount of tanning material to complete the tanning operation.

67 That improvement in methods of tanning hides and skins which comprises slicking a hide or skin out in fully extended condition upon a smooth supporting surface and simultaneously therewith removing the greater portion of the water content of the hide or skin, applying a strong or concentrated tanning material to the hide or skln while in fully extended condition, maintaining the hide or skin in such fully extended condition until it has been set in such extended condition by the tanning material, and subsequently treating the hide or skin with tanning material to complete the tanning operation.

68. That improvement in methods of tanning hides and skins which comprises applying a substantial film of liquid tanning ,material to a raw hide or skin while in fully extended condition to effect substantially instantaneous tanning of the hide or skin an to set the hide or skin in its fully extended condition, and subsequently drumming the hide or skin with a strong or concentrated tanning material to complete the tanning of the hide or skin.

69. That improvement in methods of tanning hides and skins which comprises applying a substantial film of a tanning solution not substantially lower than 100 Bkr. to a raw hide or skin to effect substantially instantaneous tanning of the hide or skin while supported in extended condition, whereby the hide or skin will subsequently maintain its extended area, and then drumming the hide or skin with a strong or concentrated tanning solution to effect complete tanning of the hide or skin. 1 v 70. That improvement in methods of tanning hides and skins which comprises applying a substantial film of tanning solution not 

